watchers

The first dragon seen in Avallore was a white dragon as it passed over the lands of humans.
The elves saw it next, as it passed over their forest.
The halflings saw it last as it descended on their villages and destroyed their homes and their people.
Some towns remained mostly intact, but most were reduced to rubble as the halflings fled into the Haridry Desert.

No dragons were seen until decades later when numerous dragons invaded all of Avallore.
They were pushed back by all but the Frost Dworcs, who were scattered from their home in Gustum and almost entirely destroyed.
Many dragons were killed, but some settled into the unclaimed lands, hidden as best they can to prevent hordes of people coming to finish them off.

Dragons are very dangerous, and can rarely be killed except by a concerted effort of hundreds of people.
When they attacked en mass, they mostly used their devastating breath weapons, but some used magic on the people they slew.
Dragons have only been seen in the standard chromatic colors: White, Blue, Black, Red and Green
Those few who have encountered dragons and survived have mentioned riddles, contests and wagers leading to their freedom.
They say if one can win a duel of wits with a dragon, and escape their treachery, a person can gain insight or knowledge from them.
They also say that dragons must have hordes of wealth lost by those who have failed.